Project on Concrete Mix Design for various grades of Concrete

1) CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLY ASH:

AIM:

To design a concrete mix of M35 grade of concrete with fly ash.

INTRODUCTION:

This project is based on the step by step procedure of mix design on M35 grade concrete with partial replacement of cement with fly ash.

I STIPULATION OF PROPORTIONING:

a) Grade designation: M35

b) Type of cement: OPC 53 grade confirming to IS 12269

c) Type of admixture: fly ash

d) Maximum nominal size of aggregate: 20mm

e) Minimum cement content: 340Kg/m³ (table 5 of IS 456-2000- exposure condition)

f) Maximum water cement ratio: 0.45 ( IS 456-2000 exposure condition)

g) Workability : 100mm (slump value for pumpable concrete)

h) Exposure condition: severe (reinforced concrete)

i) Method of placing: pumping

j) Degree of supervision: Good

k) Type of aggregate: crushed angular

l) Maximum cement content: 450kg/m³

m) Chemical admixture type: superplasticizer

II TEST DATA FOR MATERIALS:

a) cement used : OPC 53 grade confirming to IS 8112

b) specific gravity of cement : 3.15

c) Mineral admixture: Fly ash confirming to IS 8112

d) Specific gravity of fly ash: 2.90

e) chemical admixture : superplasticizer confirming to IS 9103

f) specific gravity:

    coarse aggregate= 2.74

    fine aggregate= 2.74

g) water absorption:

    coarse aggregate= 0.5%

    fine aggregate= 1.0%

h) free surface moisture:

    coarse aggregate= nil

    fine aggregate= nil

i) sieve analysis:

    coarse aggregate= table 2 of IS 383

    fine aggregate= as per grading zone II of table 4 of IS 383

III TARGET STRENGTH OF MIX PROPORTIONING:

f’ck= fck+1.65S                                                                

where, f’ck – target average compressive strength at 28 days

            fck – characteristic compressive strength at 28 days

               S – standard deviation

From the table 1 of IS 10262:2009, S= 5N/mm²

Target strength = 35+1.65(5)

                         = 43.25N/mm²

IV SELECTION OF WATER-CEMENT RATIO:

The maximum water-cement ratio for different grade of concrete is given in Table 5-IS456.

Maximum water cement ratio = 0.45

Adopted water cement ratio = 0.45

V SELECTION OF WATER CONTENT:

From Table 2 of IS1026, Maximum water content is 186 kg/m3 (for a slump of 25 to 50mm)

Above water-content is for 25 to 50mm slump but the slump we require is 100mm. hence we need to increase the water content to get the required slump for good workability. Clause 4.2 of IS1026 suggests an increase of 3% of water content from its original value for every increase of 25mm. Here we have a 50mm increase in the water content hence we have to increase the water content by 6 %.

Water content can be increased by 3% for every 25 mm increase of slump. Hence, for our required 75 mm slump water content = 186 + 6 × 186/100

                                             = 197.16 Lit

                                             = 198 Lit                   

As superplasticizer is used water content is reduced up to 20% and above.

Based on trials water content reduction of 20% is achieved.

Hence water content    = 198 x 0.80

                                     = 158.4 Lit

Adopted water content = 160L

VI CALCULATION OF CEMENT CONTENT:

Water-cement ratio = 0.45

Cement content = 160/0.45

                           = 355.55 kg/m³

                           =356 kg/m³

a) Percentage of fly ash needs to be decided based on the project required and quality of materials.

b) In some cases increase in cementitious material can be warranted. Increase in cementitious material content and it’s percentage may be based on experience and trial.

Final Cementitious Content (Cement+Fly ash)	= 356*1.1
	=391.6 kg
Minimum Cement Content required for ‘severe’ exposure	=340kg	Table 5-IS456
Adopted Cementitious content	=391.6 kg	> 340kg

 

Fly ash content requirement	= 391.6 * 0.30	30% replacement
	= 117.48 ~ 118 kg
Cement Content requirement	=Cementitious content – Fly ash
	=391.6-117.48
	= 274.12

Calculation of Super Plasticizers @ 0.6 percent to the mass of cementitious content  = 391.6*(0.6/100) = 2.35 kg

VII PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

 From Table 4, volume of coarse aggregate corresponding to 20 mm size and fine aggregate

In the present design, water-cement ratio is 0.45

Corrected volume of coarse aggregate for w/c ratio 0.45=0.63

For pumpable concrete the values are reduced by 10%

Volume of coarse aggregate = 0.63

Volume of fine aggregate = 1 - Volume of coarse aggregate

                                           = 1 - 0.63

                                           = 0.37

VIII MIX CALCULATIONS OF M35 GRADE CONCRETE:

A	Volume of Concrete	= 1 m3
B	Total Volume of Cement	= Cement/(S.G*1000)
		= 275/(3.15*1000)
		= 0.087 m3
C	Total Volume of Fly ash	= Fly ash/(S.G*1000)
		= 118/(2.5*1000)
		= 0.041 m3
D	Volume of Water	=Water /(S.G*1000)
		= 160/(1*1000)
		= 0.160 m3
E	Volume of Superplasticizers	= Superplasticizers /(S.G*1000)
		= 2.35/(1.12*1000)
		= 0.002 m3
F	Total Aggregates requirement	= A – (B+C+D+E)
		=1 -(0.087 +0.041+0.160+0.002)
		=0.71 m3
G	Coarse Aggregate (C.A)	= F * C.A ratio * S.G * 1000
		= 0.71*0.63 *2.74 *1000
		= 1225.6 kg/ m3
I	Fine Aggregate (F.A)	= F * F.A ratio * S.G * 1000
		= 0.71*0.37*2.74 *1000
		=719.8 kg/ m3

IX MIX PROPORTIONS:

S.No.	MATERIALS	QUANTITY
1	Cement	275 kg/ m3
2	Flyash	118 kg/ m3
3	Fine Aggregate	720 kg/ m3
4	Coarse Aggregate (20mm)	1226 kg/m3
5	Water	160 L
6	Superplasticizer	2 L

RESULT:

Therefore Mix Ratio of M35 Grade concrete by weight is Cement : Flyash: F.A : C.A : Water = 1:0.4:2.6:4.46:0.58

 

2) CONCRETE MIX DESIGN FOR M50 GRADE CONCRETE WITHOUT FLY ASH:

AIM:

To design a concrete mix of M50 grade of concrete without using fly ash.

INTRODUCTION:

This project is based on the step by step procedure of mix design on M50 grade concrete without using any replacements.

I STIPULATION OF PROPORTIONING:

a) Grade designation: M50

b) Type of cement: OPC 53 grade confirming to IS 12269

c) Maximum nominal size of aggregate: 20mm

d) Minimum cement content: 340Kg/m³ (table 5 of IS 456-2000- exposure condition)

e) Maximum water cement ratio: 0.45 ( IS 456-2000 exposure condition)

f) Workability : 100mm (slump value for pumpable concrete)

g) Exposure condition: severe (reinforced concrete)

h) Method of placing: pumping

i) Degree of supervision: Good

j) Type of aggregate: crushed angular

k) Maximum cement content: 450kg/m³

l) Chemical admixture type: superplasticizer

II TEST DATA FOR MATERIALS:

a) cement used : OPC 53 grade confirming to IS 8112

b) specific gravity of cement : 3.12

c) chemical admixture : superplasticizer confirming to IS 9103

d) specific gravity:

    coarse aggregate= 2.74

    fine aggregate= 2.56

e) water absorption:

    coarse aggregate= 0.5%

    fine aggregate= 1.0%

f) free surface moisture:

    coarse aggregate= nil

    fine aggregate= nil

g) sieve analysis:

    coarse aggregate= table 2 of IS 383

    fine aggregate= as per grading zone II of table 4 of IS 383

III TARGET STRENGTH OF MIX PROPORTIONING:

f’ck= fck+1.65S                                                                

where, f’ck – target average compressive strength at 28 days

            fck – characteristic compressive strength at 28 days

               S – standard deviation

From the table 1 of IS 10262:2009, S= 5N/mm²

Target strength = 50+1.65(5)

                         = 58.25N/mm²

IV SELECTION OF WATER-CEMENT RATIO:

From the table of IS 456-2000

Maximum water cement ratio = 0.35

V SELECTION OF WATER CONTENT:

From Table 2 of IS 456, Maximum water content is 186 kg/m3 (for a slump of 25 to 50mm)

Water content can be increased by 3% for every 25 mm increase of slump. Hence, for our required 75 mm slump water content = 186 + 6 × 186/100

                                             = 197.16 Lit

                                             = 197Lit

As superplasticizer is used water content is reduced up to 20% and above.

Based on trials water content reduction of 27% is achieved.

Hence water content = 197 x 0.73

                                  = 143 Lit

VI CALCULATION OF CEMENT CONTENT:

Water-cement ratio = 0.35

Cement content = 143/0.35

                           = 410kg/m³

From Table 5 of IS 456, for extreme exposure condition, minimum cement content is

360kg/m³

410kg/m³ > 360kg/m³. Hence OK

VII PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

From Table 3 of IS 10262. Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 =0.62.

 In the present case, the water-cement ratio is 0.35. Therefore. The volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. The proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio).

Therefore. The corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.

For pumpable concrete the values are reduced by 10%

Volume of coarse aggregate = 0.65 x 0.9

                                                = 0.585

Volume of fine aggregate = 1 - Volume of coarse aggregate

                                           = 1 - 0.585

                                           = 0.415

VIII MIX CALCULATIONS OF M35 GRADE CONCRETE:

A	Volume of Concrete	= 1 m3
B	Total Volume of Cement	= Cement/(S.G*1000)
		= 410/(3.12*1000)
		= 0.131 m3
C	Volume of Water	=Water /(S.G*1000)
		= 143/(1*1000)
		= 0.143 m3
D	Volume of Superplasticizers	= Superplasticizers /(S.G*1000)
		= 8.2/(1.145*1000)
		= 0.007 m3
E	Total Aggregates requirement	= A – (B+C+D)
		=1 -(0.131 +0.143+0.007)
		=0.719 m3
F	Coarse Aggregate (C.A)	= F * C.A ratio * S.G * 1000
		= 0.719*0.585 *2.74 *1000
		= 1152.48 kg/ m3
G	Fine Aggregate (F.A)	= F * F.A ratio * S.G * 1000
		= 0.719*0.415*2.56 *1000
		=763.86 kg/ m3

IX MIX PROPORTIONS:

1) Cement = 410Kg/m³

2) Water = 143Kg/m³

3) Fine aggregate = 763.86Kg/m³

4) Coarse aggregate = 1152.48Kg/m³

5) Chemical admixture = 7Kg/m³

6) Water-cement ratio = 0.35

RESULT:

Therefore Mix Ratio of M50 Grade concrete by weight is Cement: F.A : C.A : Water = 1:1.86:2.81